Periodical cicada continues to occur as expected in southeastern and southwestern Illinois. They have also been reported as being numerous in Weldon Springs State Park in DeWitt County, where members of this 13-year brood, Marlatt's Brood XXIII, would be expected. However, there has also been a cicada report from northeastern Illinois.
In 2004, the Great Eastern Brood, Marlatt's Brood X, emerges in Clark, Edgar, and Vermilion counties. The partial emergence of the Northern Illinois Brood, Marlatt's Brood XIII, occurs in 2004 in northeastern Illinois,affecting Cook County, including the western edges of Chicago, the eastern half of DuPage County, southeastern Lake County, and northeastern Will County. The main emergence of the Northern Illinois Brood occurs in 2007, covering most of the northern half of Illinois. Being more northern, the Great Eastern Brood (as well as both emergences of the Northern Illinois Brood) emerges every 17 years.
Particularly in the year preceding and that following an emergence, a few adults emerge. Both early and late-emerging individuals are called stragglers. Even fewer emerge 2 years before or after a major emergence, and that is probably the source of the cicada report from northeastern Illinois. To give an idea of the relative numbers of stragglers, Henry S. Dybas of the Field Museum in Chicago reported in 1969 that about a dozen periodical cicadas had been collected since the previous emergence in 1956. In 1956, he found 133,000 to 1.5 million per acre in various forest habitats.
Adult cicadas do little feeding, but the females in-sert their eggs through slits they make in stems up to 2 inches across. In high-emergence areas, egg-laying may weaken stems, causing them to wilt and snap in the wind. On established trees and shrubs, this causes aesthetic damage but is no real threat to overall plant health. However, oviposition into trunks up to 2 inches across can cause the trunk to snap, severely damaging or killing young trees.
We recommend against planting small transplants the year before emergence to avoid damage. Trunks of susceptible trees can be wrapped or caged to reduce egg-laying damage. Emergence will not be heavy in housing developments and other areas where the trees and shrubs were all removed within the past 50 to 100 years; such activity kills the root systems and thus the cicada nymphs feeding on them.